Set a hidden type in the form to reference which settings you want for this form.
There are two ways you can do this:
If the setting files are in the same folder as mmex.php write only the file name:
<input type="hidden" name="settings" value="Contact Form.stg">
If the setting file(s) is in a different folder than mmex.php you must write the absolute path of the settings file:
<input type="hidden" name="settings" value="http:/www.domain.com/hr/Contact Form.stg">